When Mohamedou asks detainee 'Marseille' in French if the place Marseille is located at sea (la mer), the subtitles wrongly translate 'la mer' as 'ocean'. Marseille is located at the Mediterranean Sea.
The Guards did not wear radio or MP brassards on the blocks with the detainees while on duty. This is a mistake.
The cells were not as depicted in the movie. The black stripe painted wasn't added until the spring of 2003. Also, there were no hooks or eye-bolts in the the individual cells for the detainees. The cells are also close but not exactly the same as those in the camp.
When inmate 760 gets into his cell for the first time, as he leans over his bed the microphone battery pack can be seen through his orange jumpsuit at the lower right of his back.
In the confrontation scene in the Pentagon parking lot between Benedict Cumberbatch's character and a US Marine Corps colonel both officers are wearing the large shoulder rank insignia on their garrison covers (hat) instead of the correct size smaller collar rank insignia.